1. Field of the Invention
This invention relates to trimethylolheptanes and use thereof.
2. Description of Prior Arts
Among the known trimethylolalkanes, there are 1,1,1-trimethylolalkanes, such as 1,1,1-trimethylolethane and 1,1,1-trimethylolpropane. These 1,1,1-trimethylolalkanes are used as raw materials for the production of alkyd resins, polyurethane resins and so forth. It is also known that 1,1,1-trimethylolheptane is useful as a raw material for the production of polyesters, polyurethanes and so on (Japanese Laid-open Patent Application Kokai No. 148134/1986).
When the above-mentioned 1,1,1-trimethylolalkanes, for example 1,1,1-trimethylolethane and 1,1,1-trimethylolpropane, are used as raw materials for the production of alkyd resins, polyurethane resins and so on, the three hydroxyl groups of each 1,1,1-trimethylolalkane are utilized for the formation of bonds with the functional groups of other molecular species, for example an ester bond, a urethane bond, etc. However, the three methylol groups of a 1,1,1-trimethylolalkane are bound to one and the same carbon atom and, therefore, the steric hindrance among the three hydroxyl groups is relatively high, so that the three hydroxyl groups each do not always show sufficiently high reactivity. In particular, when two of the three hydroxyl groups of a 1,1,1-trimethylolalkane each form a bond as a result of reaction with some other molecule, the remaining third hydroxyl group has considerably reduced reactivity, so that resins produced by using a 1,1,1-trimethylolalkane require a fairly long time for curing or hardening. Accordingly, one can hardly say that 1,1,1-trimethylolalkanes always have properties satisfactory for their use as raw materials in the production of resins, among others.
Polyester resins obtained by esterification of a polybasic acid and a polyhydric alcohol are in wide use in the form of fibers and also in the form of films, molding materials, coating compositions and so on. In particular, polyester resins are widely used in household paints and paints for use in building industry and other industries, among others, and are one of the most important classes of paint resins since they have luster and since, in addition, their paint characteristics can be varied fairly optionally by varying the starting material polybasic acid and/or polyhydric alcohol, the quantity ratio therebetween, the molecular weight, acid value or hydroxyl value of the resin and the quantity ratio between the resin and the curing agent, among others.
Automobile paints, for example, are required to have good chipping resistance in many instances. Precoated metal sheets are required to have good flexing resistance, and paint films applied to plastics to be resistant to cracking and breaking due to deformation of paint film-bearing plastics. Thus, there is a field in which polyester resin paints are required to have flexing resistance and flexibility.
Polyester resin-based paints have good flexing resistance by nature. As possible means of giving flexibility to polyester resins, there may be mentioned, among others, making to react with long-chain fatty acids, reducing the degree of crosslinking, or using long-chain aliphatic polybasic acids and polyhydric alcohols while reducing the quantity of aromatic acids. In actuality, however, such means cause decreases in paint film hardness, strength and/or durability and in compatibility with other resins or curing agents (hardeners). For these and other drawbacks, said means of giving flexibility each has its limit. There is a great demand for means of giving flexibility to polyester resins without impairing the above-mentioned properties, in particular hardness.
The so-called high-solid paints which contain solids in increased concentrations and solvents in decreased contents are advantageous from the energy saving and pollution control viewpoints and are in much increased demand nowadays. High-solid compositions may be obtained by using resins which do not cause any significant or excessive increase in solution viscosity even when the resin concentration is increased. Reduction in resin molecular weight is effective in preparing high-solid compositions but at the same time results in decreases in paint film characteristics in many instances. For preparing high-solid compositions, it is therefore important to have a low-viscosity resin without decreasing the molecular weight.
Curability is also an important performance characteristic of paints. Generally, paint films can have desired physical properties only after paint gelation by three-dimensional crosslinking. While unsaturated polyester resins can be cured by crosslinking reaction of double bonds, for instance, contained in themselves, curing is attained in many instances by reaction of a curing agent, such as an amino resin (aminoplast) or a polyisocyanate, with the terminal hydroxyl (--OH) groups of polyester resins. If the rate of the reaction between polyester resin hydroxyl groups and such a curing agent is slow, a long period of time is required for curing (in general terms, drying of paint). If the curing temperature is raised to promote curing, resins may be discolored or decomposed. If the rate of curing reaction is excessively fast, the curing reaction may proceed already before paint application following admixture of a curing agent with polyester resins. In such case, the paints obtained may gelate or acquire an increased solution viscosity before application, decreasing the stability of the paints. It is desirable that the curing of paint resins will not take place during storage but can proceed in the step of drying or baking as rapidly and uniformly as possible. If this curing reaction is not complete, unreacted functional groups react gradually over a long period after film formation, inducing changes in physical properties of coat films with the lapse of time. When polyhydric alcohols so far in use as branching agents for polyesters, for example glycerin, trimethylolpropane, pentaerythritol, etc., are used, the rate of curing reaction becomes slow and the curing reaction will not be complete.
In recent years, the so-called radiation-curable resin compositions capable of being cured by irradiation with ultraviolet rays, electron beams or the like have come into practical use in various paints, coating compositions, inks, printing materials, adhesives, resists, insulating varnishes, optical fibers and so on. They have rapid curability and are solvent-free and, therefore, are advantageous from the resources saving, energy saving, pollution control and high productivity viewpoints as compared with thermosetting resins. Generally, however, the radiation-curable resin compositions, which have the above-mentioned advantages, still have problems to be solved particularly with respect to toxic properties of polyfunctional polymerizable monomers (also called reactive diluents) to be used therein or to pliability, toughness and adhesion of coat films obtained after polymerization. This is one material reason why the production of such resins have not attained rapid growth contrary to expectation.
Accordingly, the advent of radiation-curable resin compositions rich in flexibility, toughness and adhesion but low in toxicity is earnestly waited for.
Meanwhile, trimethylolpropane tri(meth)acrylate is used as a polyfunctional polymerizable monomer in a very wide range and in large quantities.
However, trimethylolpropane triacrylate has a primary skin irritation index (P.I.I.) of 4.8, namely high skin irritating property. Therefore, it is necessary in handling it to use care to avoid skin contact and to prevent hazard in case of skin contact to the utmost. Furthermore, when said trimethylolpropane tri(meth)acrylate is added in large amounts, the toughness, flexibility and adhesion of coat films are much decreased.
In recent years, various fields where tough coat films having high strength and elongation or coat films having flexibility and pliability are earnestly desired have been expanding rapidly. Fields in which cured coat films are required to have satisfactory durability and low-temperature resistance also have been expanding. It is also important that a polyfunctional polymerizable monomer should have good diluting effect, good workability and good applicability.
Generally, the skin irritation mentioned above can be reduced by increasing the molecular weight of the polymerizable monomer. However, an increased molecular weight brings about an increased viscosity, whereby the diluting effect is reduced. Furthermore, the increase in molecular weight means a decrease in (meth)acryl group density; the curability and weather resistance are markedly decreased. It has thus been difficult to meet these contradictory requirements simultaneously.
Accordingly, it is an object of the invention to provide novel trimethylolalkanes having three highly reactive hydroxyl groups.
Another object of the invention is to provide certain uses of said trimethylolalkanes.
A third object of the invention is to provide, as a use of said trimethylolalkanes, polyester resins having a low glass transition temperature and rich in flexibility and low-temperature resistance.
A fourth object of the invention is to provide polyester resins with which high solid paints can be prepared and which have a low viscosity as compared with other resins comparable thereto in molecular weight.
A fifth object of the invention is to provide resins which can be brought to complete cure with ease and at a high curing rate.
A further object of the invention is to provide, as a use of said trimethylolalkanes, polymerizable monomers having a low viscosity, good dilution effect, low skin irritation, low toxicity and good curability.
A still further object of the invention is to provide radiation-curable resin compositions containing said polymerizable monomers and having good workability and good curability as well as tough coat films which are obtainable by curing said resin compositions and have good durability and low temperature resistance.
These objects as well as other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description.